We use “enough of” before determiners (such as - that, this, a, my, the) and pronouns.

Some examples:
a)I don’t know enough Japanese to translate this. (It is wrong to say – enough of Japanese)
I don’t understand enough of the words in this book.
b)You did not purchase enough food. (It is wrong to say – enough of the food)
You did not purchase enough of them.

If the meaning is clear, enough can be used alone without a noun to refer to an amount.

Some examples:
Half a kilo of sugar will be enough.
It is wrong to say “The meat is enough” – because meat is not an amount.